Given the lack of progress in talks on North Korea's nuclear weapons programme, US President Donald Trump has consulted with South Korean President Moon Jae In.

Both agreed in a telephone call on Saturday that it was necessary to continue the dialogue with the Communist leadership in Pyongyang, according to Moon's office.

Both had come to the conclusion in their 30-minute conversation that the situation was ‘serious.’ The phone call came about at the request of Trump, Moon's office said. He talked extensively with Moon about ways to advance the peace process on the Korean Peninsula.

Both agree that ‘the momentum for dialogue should be maintained in order to achieve rapid results in the negotiations on denuclearization,’ it said. Denuclearization refers to the nuclear disarmament of North Korea.

The tone between Washington and Pyongyang has recently deteriorated once again.

North Korea's First Vice-Minister of Foreign Affairs Choe Son Hui on Thursday criticized Trump's statements alluding to the possible use of military force in the nuclear dispute and again describing North Korean leader Kim Jong Un as ‘rocket man.’ Choe warned against a new war of words.

US negotiations with North Korea have not progressed since their failed February summit in Vietnam.

Pyongyang had unilaterally set a deadline by the end of the year, by which time Washington should submit new proposals.

There are fears in South Korea that North Korea could lift its moratorium on nuclear testing and long-range missile testing.